I recently picked up two Colt Sp1 Ar rifles. They had been used by the Texas Dept. of corrections. So this week I stripped them down as I plan to refinish them and restore the furniture to A1 configuration.
I cleaned both barrels with about a dozen patches soaked with Tiptons truly remarkable bore solvant. then 6 strokes with a bore brush. Then six twists with a chamber brush. A flush out with Gunscrubber. then filled the barrels with Outers Bore foam.
Patches were coming out with alot of "Blue" coloring. finally another flush with Gunscrubber and then three patches of Breakfree clp.
Question is one barrel came out pretty clean and shiney , but the other barrel still looks dirty.
Do you think this barrel is still good? I really don't want to go for another barrel as my Wife is screaming now at the money I have spent on these two project guns so far.

try JB bore paste and Kroil

Or Sweets762 bore cleaner. Very high ammonia content that really removes the copper fouling.

I bought one of these uppers from the DOC rifles, took a bit of work but it came clean. I used Hoppes and followed it up with JB Bore Paste.

You probably need to soak it for a few days, this or lots of scrubbing.